Merge "docs: Update READ_EXTERNAL_STORAGE explanation" into tm-dev am: 19a290e3 am: 8b88c5a2

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/20066630



Change-Id: Ifb18aefa861e5040b8834d3bbfd9fe0546b0c30f
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>